1. Field of the Invention
The present invention relates generally to solar battery systems for vehicles, and more particularly, to a system for supplying electric equipments provided in a vehicle with electric power produced by a solar battery mounted on a vehicle body, in which one or more of the electric equipments are selected to be supplied with the electric power so as to be driven efficiently in response to an output of electric power of the solar battery.
2. Description of the Prior Art
In the case where a vehicle, such as a passenger car, with a closed cabin is parked for hours to be exposed to the scorching heat of the sun, the temperature in the cabin may be extremely increased compared with the atmospheric temperature at the outside of the vehicle so that a driver or passenger getting on the vehicle feels uncomfortable and it takes a relatively long time to reduce the temperature in the cabin to be agreeable after an air conditioner provided in the vehicle is started to operate by the driver or passenger. For relieving such inconveniences, there has been proposed to provide a vehicle with a ventilating arrangement which includes ventilation ducts formed in a vehicle body to cause a cabin provided in the vehicle body to communicate with the outside of the vehicle and ventilating fans disposed in the ventilation ducts, respectively, and in which each ventilating fan is caused to operate for exhausting air staying at the cabin to the outside of the vehicle and taking fresh air in the cabin so as to reduce the temperature in the cabin when a difference between the temperature in the cabin and the atmospheric temperature at the outside of the vehicle reaches to a predetermined value. In the ventilating arrangement thus constituted in the vehicle, however, since the ventilating fans are usually driven by electric power supplied from a storage battery which the vehicle is equipped with, it is feared that the storage battery is subjected to an excessive load to drive the ventilating fans in the vehicle kept parking in which the storage battery cannot be charged.
Accordingly, it has been also proposed to use, in place of a storage battery, a solar battery which is operative to convert directly solar energy to electric energy in order to supply electric power for driving ventilating fans provided in such a ventilation arrangement as aforementioned, as disclosed in, for example, the Japanese patent specification published after examination under publication number 59-51451. In this case, the solar battery is mounted on a roof portion of a vehicle body to have a plurality of light receiving areas facing upward to the outside of the vehicle body so as to receive the sunlight effectively and the electric power obtained from the solar battery in response to the quantity of solar radiation supplied to the light receiving areas of the solar battery is applied to each of the ventilating fans to drive the same.
In the above mentioned ventilating system in which the solar battery is used as a power source for supplying the ventilating fans with electric power, all of the ventilating fans included in the system or some of the ventilating fans selected by a driver or passenger in the vehicle are driven at the same time by the electric power supplied from the solar battery, so that the number of the ventilating fans supplied at the same time with the electric power from the solar battery is determined without reference to variations in an output of electric power of the solar battery which varies proportional to the quantity of the solar radiation supplied to the solar battery. Then, the solar battery which produces the output of electric power proportional to the quantity of the solar radiation supplied thereto and is provided with an optimal operating point in its output characteristic may be caused to work at an operating area which does not include the optimal operating point in its output characteristic for supplying all or some of the ventilating fans selected by the driver or passenger with the electric power at the same time when the solar radiation supplied to the solar battery is relatively small, for example. In a situation wherein the solar battery is caused to work at an operating point which is apart from the optimal operating point in its output characteristic, the solar battery is not utilized efficiently and the ventilating system cannot be caused to operate effectively.
Meanwhile, a vehicle develops a tendency to be equipped with various kinds of electric equipments, such as an electric refrigerator, electric warmer, portable television receiver, radio receiver and so on, in addition to the ventilating arrangement, and since it is feared that electric power from a storage battery provided in the vehicle is running short if each of the electric equipments is driven by the electric power supplied from the storage battery in the vehicle kept parking, it has been further proposed to use a solar battery mounted on a vehicle body as a power source for driving some of the electric equipments in the vehicle kept parking. In such a case, the electric equipments are different in power consumption with each other, and when one or more of the electric equipments which are of relatively large power consumption are selected to be driven by electric power supplied from the solar battery, the solar battery may be also caused to work at an operating area which does not include an optimal operating point in its output characteristic for supplying the selected electric equipments with the electric power so as not to be utilized efficiently and therefore, if the worst happens, the selected electric equipments cannot be made to operate properly.